1. Field of the Invention
The present invention is related to the following products or methods:    (A) a relief printing plate for forming a high definition pattern by a printing method;    (B) a plate type photosensitive resin for manufacture the relief printing plate;    (C) a method for manufacturing an electric circuit pattern formed using the relief printing plate;    (D) a method for manufacturing an organic electroluminescence (EL) device;    (E) an organic EL device; and    (F) an organic EL display.
In addition, the present invention is related to the following products or methods:    (G) a relief printing plate used for manufacturing an organic electronic device;    (H) an inspection method of the relief printing plate;    (I) a method for manufacturing the organic electronic device by using the relief printing plate; and    (J) an organic electronic device.
2. Description of the Related Art
In recent years, development of electronic devices using a fine processing technique is remarkable. It is expected that such a electronic device will contribute to development in a electronics field, biotechnology field and an optronics field of the next generation.
In these days, electronic devices in practical use are mainly manufactured using inorganic semiconductors. However, hereafter, in view of reduction of manufacturing cost, power consumption of a device and higher performance of a device, it has been expected that organic electronic devices will be in practical use, the organic electronic device using a material having a property different from a property of a conventional material or especially using an organic molecule.
Among them, an organic electronic device which functions as a light emitting device is especially called an organic electroluminescence device. Especially, the organic electroluminescence device attracts attention in view of a thin device, low power consumption and light emitting characteristics.
The organic electroluminescence (EL) device is a light emitting device having an organic light emitting layer between an anode and a cathode. When a voltage is applied to the EL device, a hole is injected from an anode and an electron is injected from a cathode. When a pair of the hole and the electron recombines in a surface or an inside of the organic light emitting layer, energy is generated. The energy is taken out as light. The organic EL device in which an organic material is used for a light emitting layer has been studied from a long time ago. Since there was a problem in a light emitting efficiency, the organic EL device was not in practical use. However, C. W. Tang was proposed an organic EL device having two layer construction where an organic layer was divided into two layers of a light emitting layer and a hole transport layer. In this organic EL device, it was confirmed that light was high efficiently emitted at low voltage (See non-patent document 1). Therefore, from this time, the organic EL device has been actively studied.
An organic EL element emits light when a current is supplied to a light emitting layer which is formed from an organic light emitting material and between two opposed electrodes, and, in order to achieve efficient light emission, it is important to keep a film thickness of the light emitting layer to about 100 nm. Further, in the case of forming a display from the organic EL element, it is necessary to perform patterning on the organic EL element with high definition.
As the organic light emitting material for forming the light emitting layer, a low molecular material and a high molecular material are usable. The low molecular material is subjected to resistive heating vapor deposition and the like to form a thin film, and at the same time the patterning is performed by using a microscopically patterned mask. However, this method has a problem that patterning accuracy is reduced with an increase in size of a substrate.
That is, when patterning of a light emitting layer is performed in order to make an organic EL device full-colored, in the case where a low molecular material is used, light emitting materials of different light emitting colors is evaporated and formed on parts corresponding to desirable pixels by using a mask having patterns corresponding to desirable pixel shape. This method is superior in forming evenly a thin film of a desirable shape. However, in view of accuracy of a mask, if a substrate to be evaporated is large, it is difficult to form a pattern.
On the other hand, in the case where a high molecular material is used, pattern formation by an ink jet method and pattern formation by a printing method are mainly proposed. For example, an ink jet method disclosed in a patent document 1 is a method for forming a desired pattern by a step of discharging a light emitting material, the material being dissolved in a solvent, on a substrate from an ink jet nozzle and a step of drying the discharged material.
However, since an ink droplet discharged from a nozzle is spherical, when the ink droplet drops on a substrate, the ink spreads to circular shaped. Therefore, the shape of formed pattern lacks in linearity. In other case, since accuracy in dropping of an ink droplet is bad, there is a problem in than a linear pattern can not obtained. On the other hand, for example, in patent document 2, a method for form a linear pattern by the following processes is disclosed: a bank having an ink-repellent property is formed on a substrate by a photolithography method or the like; thereafter, an ink droplet is dropped there and the ink is repelled according to a shape of a bank; and a linear pattern is formed. However, when the repelled ink goes back inside a pixel, an ink is built up, thereby there is a remained problem in that a fluctuation of film thickness of an organic light emitting layer inside a pixel occurs.
Therefore, the high molecular material has recently been used as the organic light emitting material, and a method of forming a thin film by wet coating with a coating liquid obtained by dispersing or dissolving the organic light emitting material into a solvent has been tried. As the wet coating method for the thin film formation, spin coating, bar coating, projection coating, dip coating, and the like are known. However, the wet coating methods have difficulty in realizing the high definition patterning and color coding with R, G, and B, and it is considered that the thin film is most effectively formed by a printing process that is capable of achieving excellent color coding and patterning.
Then, an ink is made by using an organic high molecular light emitting material, instead of a low molecular organic light emitting material. A method for forming a pattern by a printing method using this ink has been proposed. In particular, a method using a resin relief printing plate, a method using a reverse type printing and a method using a screen printing has been proposed.
It is often that an organic electroluminescence element or a display uses a glass substrate as a substrate. Thus, a method to use metal hard printing plate such as a gravure printing method is unsuitable. Offset printing to use rubber blanket having elasticity and relief printing method to use rubber printing plate and photosensitive resin printing plate having elasticity are suitable. As attempt by these printing methods, a method (patent document 3) by offset printing and a method (patent document 4) by relief printing are really proposed.
Especially, a printing method using a resin relief printing plate is superior in accuracy of pattern formation and evenness of a film thickness, thereby the printing method is suitable for a method for manufacturing an organic EL device by a printing method. In addition, if a low molecule organic light emitting material can be dissolved or dispersed in a solvent, not only a high molecule organic light emitting material but also a low molecule organic light emitting material can be used for making an ink and pattern formation by a printing method using the ink is possible.
In general, in the case where a display device using an organic electroluminescence device is used, it is often that a matrix display is formed by sectioning a light emitting part into a fine pixel. When such a matrix display is manufactured by a printing method, a relief printing plate which is patterned as a delta shape or a stripe shape, the shape being corresponding to a shape of a pixel, is used. In this case, if a relief printing plate has a defect, a pattern printed on a substrate by using this relief printing plate also has a defect. This causes a defective device. In a display device, checking by comparison of patterns by an optical checking is generally performed for checking if a defect in a pattern exists or not. In this method, a matrix pattern image formed on a substrate while transmittance light or reflection light is irradiated is taken by a line sensor or an area sensor. In each pixel of a matrix, a pixel is compared with an adjacent pixel if a pattern of the pixel is same or not. If shapes of the patterns are same, the test result is good. If shapes of the patterns are different, it is thought that a defect such as an included undesirable material or a void in a pixel occurs.
However, in the case where this checking method is applied to a pattern formed substrate of an organic electroluminescence device, an organic light emitting layer or an organic light emitting assist layer formed on a substrate is irradiated with strong light. In general, an organic light emitting layer used for an organic electroluminescence device is weak for strong light. The characteristics of the organic electroluminescence device may become bad by irradiation light at the time of the checking. In addition, if the characteristics do not become bad, it is difficult to check the device because it is difficult to obtain sufficient contrast at the time of optical checking. This is because film thicknesses of an organic light emitting layer and an organic light emitting assist layer are thin, about several tens nm, thereby absorption of light at the layers is small. Therefore, it is important to perform optical checking of a relief printing plate used for forming a pattern.
On the other hand, in the structure of a relief printing plate used for forming a pattern of an organic electroluminescence, it is desirable that a metal material be used for a base material in view of position accuracy of a pattern of a relief printing plate as shown in a patent document 5 by the inventor of the present invention. In addition, it is desirable that a convex part of a relief printing plate, the part being formed on a base material, be formed of a resin such as a resin shown in a patent document 6 and a patent document 7 by the inventor of the present invention. According to these inventions, since a relief printing plate has a metal substrate and a resin relief printing layer on the metal substrate, it is necessary for the pattern of the resin relief printing layer on the metal substrate to be checked if the pattern has a defect or not. However, in the case where the defect check is performed for a fine pattern on a metal substrate by a comparison checking, it is difficult to recognize a defect. This is because diffusely reflection from a surface of a metal under the resin pattern is stronger than an image contrast obtained by the resin pattern.
Hereinafter, the known documents are described.
[non-patent document] C. W. Tang, S. A. VanSlyke, Applied Physics Letters, vol. 51, p. 913 (1987)
[patent document 1] JP-A-H10-12377
[patent document 2] JP-A-2002-305077
[patent document 3] JP-A-2001-93668
[patent document 4] JP-A-2001-155858
[patent document 5] Japanese Patent Application No. 2006-179160
[patent document 6] Japanese Patent Application No. 2006-268872
[patent document 7] Japanese Patent Application No. 2006-268873
[patent document 8] JP-A-2004-70231